Giardiasis

Clear→ stable

Gastrointestinal

Current NYS Status

2,493 cases in 2024 — near the 5-year baseline of ~5,191.

2024 statewide cases: 2,493

Source: NYSDOH Annual Communicable Disease Report 2024 + 5-yr baseline

What is it?

Giardiasis is caused by Giardia intestinalis (also called G. lamblia or G. duodenalis), a microscopic parasite that lives in the intestines. NYS had 2,493 cases in 2024. It is one of the most common causes of waterborne disease in the US and a frequent culprit in backcountry water sources.

How it spreads

Spreads through swallowing contaminated water (lakes, streams, pools), eating contaminated food, or direct fecal-oral contact with an infected person or animal. Common in childcare centers and among hikers who drink unfiltered backcountry water.

Symptoms

Diarrhea (often greasy and foul-smelling), gas, stomach cramps, nausea, dehydration, and weight loss beginning 1–3 weeks after exposure. Some people carry Giardia with no symptoms but can still spread it to others.

Who is at risk?

Hikers and campers who drink unfiltered water, children in daycare settings, international travelers, and people who have close contact with infected individuals or animals.

What you can do

🛡Always treat backcountry water before drinking — use a filter, boil for 1 minute, or use chemical treatment (iodine or chlorine dioxide)

🛡Wash hands thoroughly after using the toilet and before preparing food

🛡Keep children with diarrhea out of pools and water play areas

⚕️See a provider if diarrhea lasts more than a week — effective antibiotic treatment (metronidazole, tinidazole) is available

Tier B — Annual report tracking

Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.

Seasonality: year round

This information is for general public health awareness and is not a substitute for professional medical advice, diagnosis, or treatment.